Bridges

The West Gate Tunnel Project is one of Australia’s largest infrastructure projects providing a much-needed alternative crossing of the Yarra River to the West Gate Bridge. The project includes twin bored tunnels and a significant length of bridge viaducts. 14 km of new shared user paths (SUP) have been constructed as part of this project to improve commuter accessibility and safety. This bridge is located on the section of a shared user path commencing from the Spotswood train station and travels at grade until Stoney Creek, where it is carried by a 3-span simply supported bridge, and then the remaining section runs at grade to connect onto the existing Stony Creek Reserve SUP.

There is a significant height of approach embankment fill behind the abutments. Construction of the temporary working platform on Stony Creek embankment, surcharge loading from the temporary working platform and build-up of surface finish level at the back of the abutment resulted in an unacceptable deformation of the bridge after completion of construction. The consolidation of the soil, and consequent movement are expected to occur over the 100-year bridge design life as the geology underlying the footprint of the bridge comprises layers of Coode Island Silt. The ongoing lateral deformation of the soil over the life of the bridge results in imparting an unacceptable level of forces onto the bridge foundations.

Therefore, the solution to mitigate the impact on the bridge was to integrate the super and substructure on the basis that this will limit the lateral deflection of Pier 2 and Abutment AB by mobilising Pier 1 and Abutment AA to act together with the deck.